A great portion of man made energies are used up in heating and cooling. For example, a large portion of utility bills in summer are often associated with energies used up in running air-conditioners to keep the indoor temperatures low whereas, during the winter, energies are used up in running heaters to maintain indoor warm. Most of the wasted energies in heating and cooling can be attributed to a poor insulation against heat loss. In most prior arts on heat resistant paints, an ordinary paint is turned into a heat resisting paint by blending with it particulates and voids. In other similar prior arts, colloidal particulates are blended in film-forming filler materials, wherein such materials are applied over substrates like windowpanes and glasses to block infrared electromagnetic waves.
One class of prior arts on heat blocking technologies involve heat resistant paints. In U.S. Pat. No. 4,623,390, glass microspheres or hollow glass extenders are blended in an ordinary paint to reduce a direct thermal conductivity, which greatly improves insulation against heat loss. In one embodiment, glass microspheres of diameters ranging from approximately 50 microns to 150 microns are blended in an ordinary paint whereas, in an another embodiment, glass microspheres of approximately 100 microns in diameters are blended in an ordinary paint. Otherwise, U.S. Pat. No. 4,623,390 does not discuss on any aspects of the multi-layered coating structures discussed in the present invention.
In U.S. Pat. No. 8,287,998 B2, hollow microspheres selected from glass, ceramic, and organic polymer microspheres of mean particle sizes between 0.5 microns and 150 microns are blended in an ordinary paint to reduce the direct thermal conductivity. Furthermore, U.S. Pat. No. 8,287,998 B2 also incorporates infrared reflective pigment materials in an ordinary paint mixture to reduce thermal conductivity associated with radiative heat transfers. Otherwise, U.S. Pat. No. 8,287,998 B2 does not discuss on any aspects of the multi-layered coating structures discussed in the current invention.
In U.S. Pat. No. 2010/0,203,336 A1, a solar reflective roofing granule is disclosed. In one embodiment, a solar reflective granule is formed by sintering ceramic particles, wherein the sintered ceramic particles are coated with solar reflective particles. Otherwise, U.S. Pat. No. 2010/0,203,336 A1 does not discuss on any aspects of the multi-layered coating structures covered in the present disclosure.
In U.S. Pat. No. 2013/0,108,873 A1, a roofing granule forming particle is coated with a nanoparticle layer which reflects near infrared radiation. Similarly, in U.S. Pat. No. 2013/0,161,578 A1, a roofing granule is formed from an infrared reflecting inert mineral core particle which has naturally occurring voids (or defects). Otherwise, neither U.S. Pat. No. 2013/0,108,873 A1 nor U.S. Pat. No. 2013/0,161,578 A1 discuss on any aspects of the multi-layered coating structures portrayed in the current disclosure.
In U.S. Pat. No. 2008/0,035,021 A1, a method for fabricating aluminum phosphate hollow microspheres is disclosed. It also illustrates how such particulates can be utilized to improve insulation against heat loss. Otherwise, U.S. Pat. No. 2008/0,035,021 A1 does not discuss on any aspects of the multi-layered coating structures covered by the present invention.
In U.S. Pat. No. 2007/0,298,242 A1 a lens for filtering optical waves is disclosed, wherein the metallic nano-particulates comprising thin-film layers are formed on the lens surface. Otherwise, U.S. Pat. No. 2007/0,298,242 A1 does not discuss on any aspects of the multi-layered coating structures discussed in the present disclosure.
In U.S. Pat. No. 2007/0,036,985 A1, indium tin oxide (ITO) fine particulates are blended with a film-forming mixture to form a thin-film layer which reflects infrared waves. Otherwise, U.S. Pat. No. 2007/0,036,985 A1 does not discuss on any aspects of the multi-layered coating structures illustrated in the present invention.
In U.S. Pat. No. 2013/0,266,800 A1, a method for preparing aluminum-doped zinc oxide (AZO) nanocrystals is disclosed. It further discloses a thin-film structure for reflecting infrared waves which utilizes the AZO nano-particulates. Otherwise, U.S. Pat. No. 2013/0,266,800 A1 does not discuss on any aspects of the multi-layered coating structures discussed in the present disclosure.
The present invention is particularly similar to U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2, wherein multi-layered thin-film structures utilizing colloidal particulates to reflect infrared electromagnetic waves are disclosed. There are, however, fundamental differences between this invention and the foregoing prior arts which are noticeable. They are summarized below.
Following are the specifications of U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2:                1. In U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2, particulates in each layer of multi-layered structure are arrayed at regular lattice spacing.                    a) This is a must requirement; without it, the entire working principle, as described in the specifications of U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2, fails.            b) Such prior art can be classified as photonic crystals.                        2. U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2 relies on the Bragg's law for the description of infrared wave reflections.                    a) Within the frame work of Bragg's law, the lattice constant (or lattice spacing) determines the wavelength of reflected waves.            b) This is a characteristic typical of photonic crystals.                        3. In order to make the visible wavelengths highly transparent, U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2 require the following restrictions:                    a) The refractive index of particulates and the refractive index of a filler material intervening in spaces between the particulates must be nearly identical.            b) The difference between the refractive index of a filler material and the refractive index of particulates is less than or equal to 0.05. That is, if nm=1.5 is the refractive index of a filler material, then particulates must be chosen from materials with refractive indexes between np=1.45 and np=1.55 such that |nm−np|≦0.05.            c) Such restriction forbids the use of metallic particulates, which include aluminum, chromium, cobalt, copper, gold, iridium, lithium, molybdenum, nickel, osmium, palladium, platinum, rhodium, silver, tantalum, titanium, tungsten, and vanadium. On the other hand, most of the oxide materials have refractive indexes between np=1.45 and n1=1.55, and therefore can be used for the particulates.                        4. In U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2, the infrared reflection strongly depends on the incoming wave's angle of incidence, a characteristic typical of photonic crystals and a consequence of the Bragg's law.        
Following are the specifications of the present invention:                1. In the present invention, particulates are randomly distributed in each layers of the multi-layered coating system.        2. The present invention relies on the Mie scattering theory for the description of infrared wave reflections.        3. In the present invention, particulates are preferably chosen from conductors. Unlike in the case of U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2, the filler material and the randomly distributed particulates are not required to have nearly identical refractive indexes.        4. In one or more exemplary embodiments of the present invention, randomly distributed voids are also present along with randomly distributed particulates in each layers of the multi-layered coating system.        5. In the present invention, the infrared reflection has no dependence on the incoming wave's angle of incidence, a characteristic which is typical of systems involving randomly distributed particulates (with or without randomly distributed voids).        
Such noticeable differences in the specifications clearly distinguishes the present invention from U.S. Pat. Nos. 7,760,424 B2 and 8,009,351 B2.
The following prior arts on quantum dot technologies are listed here for reference: U.S. Pat. Nos. 8,362,684 B2, 8,395,042 B2, U.S. Pat. No. 2013/0,003,163 A1, and U.S. Pat. No. 2013/0,207,073 A1. Although these prior arts are technologically unrelated to the present invention, there are remarkable similarities in the distribution of particulates in each layers of multi-layered system. Otherwise, the present disclosure and the listed prior arts on quantum dot technologies are based on fundamentally different physics and two should not be overseen as the same.